Hydrocarbon conversion process to produce gasoline from high boiling hydrocarbon oils by hydrocracking and reforming



Jan. 16, 1968 R SCHOENFELD 3,364,132

HYDROCARBON CONVERSION PROCESS TO PRODUCE GASOLINE FROM HIGH BOILINGHYDROCAHBON OILS BY IIYDROCRACKING AND REFORMING Filed Sept. 19, 1966 QR m K N v, o Q n w "a m a M Fracf/onalar N N "a 4 m u v \1 I Q O "Q 4Depentam'zer i J Q i Compressor R 0 E -1 g Reactor f i w a N N a N VE NT0,?-

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United States Patent 3,364,132 HYDROCARBON CONVERSION PROCESS T0 PRO-DUCE GASOLINE FROM HIGH BOILING HY- DROCARBON OILS BY HYDROCRACKING ANDREFORMING Jack R. Schoenfeld, Oak Park, Ill., assignor to Universal OilProducts Company, Des Plaines, lll., a corporation of DelawareContinuation-impart of application Ser. No. 384,112, July 21, 1964. Thisapplication Sept. 19, 1966, Ser. No. 589,155

4 Claims. (Cl. 208-60) This invention is a continuation-in-part of mycopending application Ser. No. 384,112 filed July 21, 1964, nowabandoned. This invention relates to the production of high octanegasoline. More specifically, this invention relates to the conversion ofheavier hydrocarbons into lighter gasoline boiling range hydrocarbonshaving a high octane number without excess production of lighthydrocarbons, such as butane. Still more specifically, this inventionrelates to a process for the conversion of heavy hydrocarbons into highoctane gasoline which process comprises hydrocracking the heavyhydrocarbons into gasoline boiling range, reforming said gasolineboiling range components to a moderate octane number and contacting thenormally liquid reformate with a molecular sieve sorbent selective fornormal aliphatic hydrocarbons thereby producing a relatively less sorbedfraction having a high octane number.

In one of its embodiments this invention relates to a process for theproduction of high octane gasoline which comprise contacting a heavyfeed stock with a hydrocracking catalyst in a reaction zone maintainedat hydrocracking conditions; withdrawing a hydrocracking reactoreffluent and separating said efiiuent to produce a gasoline boilingrange fraction suitable for reforming; introducing said fraction intocontact with a reforming catalyst in a reaction zone while maintainingsaid reforming zone at mild reforming operating conditions; withdrawingfrom the reforming unit a normally liquid reformate of moderate octanenumber; introducing said reformate into a sorption unit containing asolid molecular sieve sorbent selective for normal aliphatichydrocarbons; withdrawing and recovering from said sorption unit arelatively less sorbed raffinate having a high octane number; andWithdrawing and recovering a selectively sorbed sorbate having a highconcentration of normal aliphatic hydrocarbons as a separate effluentfrom said adsorbing unit.

Since the advent of the internal combustion engine, there has been atrend in the refinery industry to increase the yield of gasoline fromcrude oil. Various cracking processes have been discovered to accomplishthis objective as is evidenced by the history of the petroleum processdevelopments. Starting with thermal cracking, improvements were made toimprove the selectivity of the cracking reactions which lead to thedevelopment of the wellknown cat crackers. Recently further improvementsin the yield and selectivity have been made by the hydrocrackingprocess. Unlike the prior processes, hydrocracking means crackinghydrocarbon molecules in the presence of excess hydrogen such that thereoccurs a rapid hydrogenation of the broken carbon to carbon bondresulting in enhanced yields and selectivity. One of the problems ofthis new hydrocracking process is the excessive production of butane. Acertain quantity of butane is desirable in finished gasoline for vaporpressure purposes. Hydrocracked gasolines generally have too low anoctane number to be useful directly in todays internal combustionengines and usually these hydrocracked gasolines are reformed to upgradethe octane number. The reforming step also produced butane and thecombined butane from the hydrocracking and reforming steps generally3,364,132 Patented Jan. 16, 1968 exceeds the required butane for vaporpressure purposes in the finished gasoline. This excess butane is onlyuseful as a direct burning fuel such as in L.P.G. and accordingly has alower dollar value. Other light hydrocarbons such as methane, ethane andpropane are also too light and volatile to be used in gasoline andaccordingly have limited use as direct burning fuels.

It is known that normal paraflins in the gasoline boiling range have lowoctane numbers. If the normal paraffin components of gasoline areextracted from the gasoline, there would be a substantial increase inoctane number. For example, normal hexane has an F-l clear octane numberof 24.8, normal heptane has an F-l clear octane number of 0.0 and normaloctane even lower. Todays engines need gasolines having at least anoctane number of and as much as and any appreciable concentration ofnormal paraflins in the gasoline results in a substantial depression ofthe octane number.

Reforming of gasoline helps to reduce the concentration of normalparaffins in most gasolines by reactions such as isomerization,hydrocracking and dehydrocyclization. In the isomerization reaction, ifthere is an excess concentration over equilibrium of normal parafiins,the normals will be isomerized to their more highly branched isomerswith a resulting increase in octane number. For example, convertingnormal hexane to 2-methyl pentane increases the F-1 clear octane numberto {73.4. In the hydrocracking reaction the higher molecular weightmolecules are cracked into lighter components with an increase in octanenumber although there is a decrease in yield. For example, if normalheptane is converted into normal pentane and ethane, the resultingnormal pentane has an F-l clear octane number of 61.8 while the ethanewould be removed from the gasoline since it is too volatile a component.This reforming hydrocracking reaction has the undesirablecharacteristics of causing a yield loss and consuming hydrogen.Generally, as a reforming catalyst reactivates, the temperatures of thereforming reactor are increased to maintain a constant octane numberwhich has the effect of increasing the amount of hydrocracking thatoccurs. In the dehydrocyclization reaction a normal parafiin would beconverted to an aromatic molecule with an evolution of four moles ofhydrogen and a substantial increase in octane number. For example,normal heptane might be converted into toluene having an F-l clearoctane number of 119.7. Unfortunately, this latter reaction is slow andoccurs only to a limited ex tent, if at all.

Thus, looking at the overall effect of the reforming reactor, thehydrocracking reaction results in the production of light hydrocarbonssuch as ethane, propane and butane while increasing the octane number,said light hydrocarbons being an undesirable product. It would bepreferable to minimize the reforming hydrocracking reaction consistentwith achieving the desired octane number.

Recently separation processes selective for normal aliphatichydrocarbons have been developed employing molecular sieve zeoliteshaving pore sizes of about 5 Angstrom units. Such a separation processcan be com bined with a hydrocracking process and a reforming process toselectively extract the low octane number normal parafiins leaving agasoline of enhanced octane number with the hydrocracker removingmaterial such as sulfur and nitrogen to maintain sieve stability andreforming catalyst stability. This will permit the reforming reactor tobe operated at milder conditions, i.e. lower temperatures, to maintainthe same octane number While minimizing the undesirable reforminghydrocracking reaction.

It is accordingly an object of this invention to convert heavyhydrocarbons to high octane gasoline while minimizing the formation oflight hydrocarbons selected from the group consisting of methane,ethane, propane and butane.

It is another object of this invention to obviate the above-mentioneddifficulties in producing high octane gasoline from heavy hydrocarbons.

It is a further object of this invention to disclose a combinationhydrocracking-reforming-separation process to efiiciently produce highoctane gasoline.

It is a more specific object of this invention to minimize theproduction of butane when converting heavy hydrocarbons boiling abovethe gasoline boiling range into high octane gasoline.

It is another more specific object of this invention to disclose acombination hydrocracking-reforming-separation process to produce highoctane gasoline While maintaining butane balancethat is, only to producesufficient butane to satisfy the vapor pressure requirement of thegasoline.

It is still another more specific object of this invention to producehigh octane gasoline from a once through reformer maintained at mildreforming conditions.

It is a further more specific object of this invention to produce astream of high purity normal paraflins in the gasoline boiling rangesuitable for use as a high quality fuel, in the production of polymersand plasticizers and as an intermediate in the production of chemicals.

The hydrocracking step of the process is carried out by passing theheavy hydrocarbon charge stock over a fixed bed of hydrocrackingcatalyst in the presence of hydrogen at elevated temperatures andpressure. A preferable hydrocracking catalyst is a refractory oxidesupport comprising silica and alumina and having incorporated thereon ametal having appreciable hydrogenation activity. Suitable supportscomprise amorphous silica-alumina, crystalline aluminosilicates such asfaujasite and mordenite (preferably in the hydrogen form), etc. Saidmetal comprises platinum, nickel, cobalt, molybdenum, iron, tungsten,palladium etc. The amorphous refractory oxide support 'may be preparedby oil dropping techniques to form spherical particles or may beprepared in pellet form using pilling machines. The crystallinealuminosilicate may be prepared by crystallization from suitable basicsolutions containing sodium cations and anions selected from the groupconsisting of silicate, aluminate and hydroxyl. The metal may then beimpregnated or ion-exchanged upon the refractory oxide as a metal saltand activated by oxidation. The finished catalyst is loaded into a fixedbed reactor and the heavy hydrocarbon is passed through said fixed bed.The reactor is maintained at temperatures of from about 550 F. to about900 F., depending upon the charge stock, the reactor pressure, the spacevelocity'and the desired degree of conversion. The pressure should bemaintained at least as high as 500 p.s.i.g. and preferably from 1,500p.s.i.g. to 2,000 p.s.i.g. It is necessary to maintain excess hydrogenin the reactor such that when a carbon to carbon bond is broken,hydrogen is available to react with the broken bond. This may beachieved by recycling separator gas which is rich in hydrogen andsupplying additional makeup hydrogen to satisfy the hydrogenconsumption. Gas rates of at least 2,500 standard cubic feet per barrelof heavy charge (s.c.f./bbl.) and preferably 5,000 to 50,000 s.c.f./bbl.should be supplied to the reactor. Liquid hourly space velocities offrom about to about 0.5 may be employed. The reactor effluent isseparated such that a fraction suitable for reforming is produced. Suchfractions preferentially have as the lightest component at least sixcarbon atom molecules and a maximum Engler distillation end point ofabout 400 F. It is preferable to employ a two stage hydrocrackingprocess, the first stage substantially converting organic nitrogen intoammonia and organic sulfur into hydrogen sulfide and the second stagesubstantially hydrocracking the hydrocarbons to produce a gasolineboiling range material. Preferable first stage catalysts comprise aGroup VI and a Group VIII metal on amorphous silica-alumina supportssuch as nickel-molybdenum or nickel-tungsten on silica-alumina.Preferable second stage catalysts comprise a Group VIII metal oncrystalline alumina-silicate such as nickel, palladium or platinum onfaujasite or mordenite.

Suitable charge stocks for the hydrocracking step comprise heavyhydrocarbon streams A preferable stock would be gas oil having aninitial boiling point of at least 400 F. and having an end point as highas about 900 F. to about 1000" F. Cycle oils from catalytic crackers andcokers would be another preferable charge stock. Middle distillates andeven kerosenes can also be used as charge stocks. Of course, mixtures ofthe above may also be used.

The reforming step of the process is carried out by passing the gasolineboiling range fraction of the hydrocracking reactor effluent over afixed bed of reforming catalyst in the presence of hydrogen at elevatedtemperature and pressure. Preferred reforming catalysts comprise analumina support having platinum and combined halogen, especiallycombined fluorine and/ or combined chlorine deposited thereon. Thealumina-combined halogen particles may be prepared by oil droppingtechniques to form spherical particles and thereupon drying andoxidizing the particles. The platinum is thereafter impregnated upon theparticles as a metal salt and activated by oxidation. The finishedcatalyst is loaded into a fixed bed re actor and the gasoline boilingrange feed is passed through said fixed bed. Reformers areconventionally maintained at temperatures of from about 850 F. to about1050 F depending upon the charge stock, the reactor pressure, the spacevelocity and the desired octane number. Typical reforming pressures varyfrom 500 p.s.i.g. to 200 p.s.i.g., depending primarily upon the chargestock. It is necessary to maintain excess hydrogen in the reactor toavoid the formation of undesirable side products such as carbon aceousdeposits. Said excess hydrogen may be supplied by recycling separatorgas which is rich in hydrogen. Gas rates sufiicient to give a hydrogento charge ratio of at least 2 and preferably at least 3 up to about 15should be supplied to the reactor. Liquid hourly space velocitiesgenerally run from 5.0 to 0.5, depending primarily upon the charge stockand the desired octane number. The normally liquid reforming reactoreflluent, called the reformate, is separated from the total effluent andis charged to the separation process step.

Part of the essence of this invention involves the opera tion of thereforming reactor at mild conditions to produce a reformate of moderateoctane number and then to extract the normal paraflins out of thereformate thereby increasing the octane number of the relatively lesssorbed raffinate stream hereinafter described. By mild conditions I meanprimarily reducing the temperature of the reactor to range of from about800 F. to about 980 F. In certain cases it might also be possible toincrease the space velocity in the reforming reactor to a minimum of 1.0and as much as 5.0. In other cases lower pressures are contemplated aspart of the mild conditions.

A preferable separation apparatus is shown in U.S. Letters Patent No.2,985,589, issued on May 23, 1961. The separation step of this inventionemploys a fixed bed of solid sorbent selective for normal parafiins andpreferably is operated in a simulated countercurrent flow of solid andliquid processing scheme. The simulated countercurrent flow is achievedby means of a rotary valve such as is described and claimed in U.S.Letters Patent No. 3,040,-' 777, issued on July 26, 1962. One of theessential parts of the separation step is the sorbent contacting chambershown in the figure. Said chamber is capable of having introduced to itcontinuously the reformate feed and a desorbing fluid whilesimultaneously having Withdrawn a relatively less sorbed high octaneraifinate and a sorbent rich in normal paraflins. This separation stepmay be carried out by introducing said reformate into a first zone of afixed bed of solid sorbent, selective for normal aliphatic hydrocarbons,containing at least four serially interconnected zones having fluid flowconnecting means between adjacent zones and between the outlet of oneterminal zone and the inlet of the other terminal zone in the series tothereby provide cyclic fluid flow in said process, substantiallysimultaneously withdrawing relatively less sorbed raflinate having ahigh octane number from a second zone immediately downstream of saidfirst zone, substantially simultaneously introducing a desorbing fluidinto a third zone immediately downstream of said second zone,substantially simultaneously withdrawing resulting sorbate comprisingselectively sorbed normal aliphatic hydrocarbons from a fourth zoneimmediately downstream of said third zone, continuously circulating astream of fluid through said series of interconnected zones, andperiodically advancing downstream the point in said fixed bed ofintroducing said reformate while simultaneously and equally advancingdownstream the point of introducing desorbent and withdrawing raflimateand sorbate.

The sorbent contacting chamber is operated at conditions of temperature,pressure and under other process conditions which depend upon theparticular feed stock involved and the required purity of product.Although this chamber may be operated either in the liquid phase orvapor phase, it is preferable to operate in the liquid phase. Typicalliquid phase operation is, for example, temperatures of from 30 F. to500 F. and more preferably from 100 F. to 380 F., and pressures of fromslightly superatmospheric to 30 atmospheres or even higher. Generallyhigher pressures will be employed for lower molecular weight feed stocksor desorbents to maintain liquid phase in the contacting chamber. Themaximum charge rate of feed stock through the fixed bed of solid sorbentis limited by the tolerable pressure drop through said fixed bed and therates of sorption. The minimum charge rate of feed stock through saidfixed bed is limited to a rate suflicient to avoid back mixing (i.e., tomaintain substantially plug flow through said beds). It is expected thatliquid hourly space velocities (on solid sorbent) of from about 0.01 toabout 20 will be employed depending upon the operating conditions ofpressure and temperature, the feed stock and the equipment limitations.In order to maintain sieve stability it is preferable that polarcompounds such as sulfur, nitrogen and oxygen compounds be removed fromthe feed to the contacting cham ber. The hydrocracking step of thisinvention is satisfactory to accomplish this result.

Suitable sorbents would be any substance which can be produced indiscrete particles within the size range of from about to about 200 meshand which have an appreciable degree of selectivity for normalparafiins. One suitable sorbent is dehydrated crystalline metallicaluminosilicate, commonly called molecular sieves. These molecularsieves are made up of a crystalline structure having many small cavitiesconnected by still smaller pores of uniform size. Although molecularsieves may be made in pore sizes of from 3 Angstrom units up to 12 or oreven more Angstrom units, the pore size should be about 5 Angstrom unitsin order to selectively sorb normal parafiins. One preferable molecularsieve is the so-called Type A (calcium form) sieve described in US.Patent 2,882,243.

Suitable desorbents comprise normally liquid hydrocarbons having aboiling point outside of the boiling point range of the feed to thecontacting chamber and an appreciable concentration of normal aliphatichydrocarbons (at least The desorbent may then be easily removed from theratfinate and the sorbate by ordinary simple fractionation and isgenerally recycled back to the sorbent contacting chamber.

One preferable embodiment is shown in the accompanying figure. It shouldbe recognized that there are numerous variations in the basic flowscheme shown and it is not intended to limit the scope of this inventionto the shown arrangement in the figure. For example, reformatefractionator 23 could precede depentanizer 12 or depentanizer 12 couldbe debutanizer or a dehexanizer; or the hydrocracking reactor may beoperated at suflicient severity to not produce any heavy product, thusobviating the need for fractionator 23, or a two stage hydrocracker asdescribed hereinbefore can be employed. Also for simplification of thedrawing and of the description, conventional equipment such as controlinstruments for observing and controlling temperatures, pressures, flowrates and liquid levels and the like, pumps, valves, and various heatexchangers are not indicated or described specifically. Further, methodsof economically and efliciently using the heated and cooled streams arenot shown. This conventional equipment is within the skill of anengineer and is omit-ted to avoid unduly describing incidental detailsto the main invention.

The heavy hydrocarbon feed stock is introduced into flow conduit 1 whereit joins flow conduit 4 carrying recycled separator gas and makeuphydrogen. The mixture flows through flow conduit 5 and entershydrocracking reactor 6 containing hydrocracking catalyst. The reactoreflluent leaves through flow conduit 7 and enters high pressureseparator 8. The normally gaseous effiuent is drawn through flow conduit9 by means of recycle compressor 10, through flow conduit 3 where itjoins the makeup hydrogen flowing in flow conduit 2 and the mixturemoves into flow conduit 4. The normally liquid efflucnt leaves separator8 where it flows through flow conduit 11 and into depentanizer 12. It isnormally preferable to depentanize prior to reforming since thereforming reactions can do very little to improve octane number of theisomers of pentane and cyclization of pentane seldom occurs. Theoverhead fraction having pentane as its heaviest component is removedthrough flow conduit 13 where it enters overhead receiver 14. Thisoverhead stream may be subject to partial condensation and the lightcomponents such as hydrogen, methane, ethane, etc., and contaminantssuch as hydrogen sulfide, ammonia, etc., are removed through flowconduit 17. A portion of the condensed overhead is returned tofractionator 12 as reflux by means of flow conduit 15. The net liquidoverhead comprising pentane and some butane is removed through flowconduit 16. The bottoms fraction having hexane as its lightest componentis removed through flow conduit 18 where a portion of the bottoms passesthrough flow conduit 19, heater 20 and returns to fractionator 12 bymeans of flow conduit 21. The net bottoms is withdrawn through flowconduit 22 where it flows into fractionator 23.

The overhead fraction from fractionator 23 is removed through flowconduit 24 where it flows into overhead receiver 25. This overheadstream comprises a material within the gasoline boiling range havinghexane as its lightest component in any significant concentration andhaving an Engler distillation end point no higher than about 400 F. Aportion of the overhead is returned to fractionator 23 by means of flowconduit 26 as reflux, while the net overhead stream is removed throughflow conduit 27 where it is sent to reforming reactor 35. The bottomsfraction of fractionator 23 is removed through flow conduit 28 where apotion flows through flow conduit 29, heater 30 and returns tofractionator 23 by means of flow conduit 31. The net bottoms is removedthrough flow conduit 32 and comprises a hydrocarbon fraction suitablefor use as a kerosene or middle distillate. If desired, this stream canbe recycled to hydrocracking reactor 6 so as to increase the gasolineyield or it may be used directly as a product. This heavy product hasmany desirable burning characteristics such as a high smoke point andcomprises a superior premium heavy fuel. The ratio of the heavy productto the gasoline range product is determined by the hydrocrackingoperating conditions of pressure, temperature, liquid hourly spacevelocity,

7 hydrogen to oil ratio and the charge stock. Generally any ratio may beproduced depending upon such economic factors as time of season,marketing demands and type of climate.

The gasoline boiling range fraction flowing in flow conduit 27 joinsrecycled separator gas flowing in flow conduit 33 and the mixture flowsinto reforming reactor 35 by means of flow conduit 34. The oil and gascontact the reforming catalyst in reactor 35 and the effluent iswithdrawn through flow conduit 36 and into high pressure separator 37.The normally gaseous eflluent is withdrawn from conduit 38 where aportion is recycled through flow conduit 39, recycle compressor 81 andinto flow conduit 33 where it ultimately returns back to reactor 35.Since the reactions present in a reformer produce hydrogen and otherlight hydrocarbon gases, the net gas is removed through flow conduit 40.The normally liquid eflluent is withdrawn through conduit 41 whereuponit enters stabilizer 42.

An overhead fraction is removed from stabilizer 42 through flow conduit43 where it enters overhead receiver 44. A portion of the overhead isreturned to stabilizer 42 as reflux by means of flow conduit 45 whilethe remaining portion is withdrawn through flow conduit 46. Thestabilizer may be operated to remove butane and remaining lightercomponents or it may also be utilized to remove pentanes in addition tothe butane and lighter components. The decision would depend primarilyupon whether normal pentane is desired in the finished gasoline.Normally, the stabilizer is operated as a debutanizer but since theseparation step will extract the normal pentane out of the gasolinefraction, it is preferable to remove all the pentanes overhead in thestabilizer and recombine the pentanes with the finished high octanegasoline. The bottoms fraction comprising the depentanized reformate isremoved through flow conduit 47 where a portion flows through fiowconduit 48, heater 49 and returns to stabilizer 42 by means of flowconduit 50. The net bottoms fraction is withdrawn through flow conduit51 where it continuously passes through rotary valve 79 and enterssorbent contacting chamber 80 at the upstream point of zone I.

Desorbent, from a source hereinafter described, continually flowsthrough flow conduit 78 through rotary valve 79 and enters sorbentcontacting chamber 80 at the upstream point of zone III. Relatively lesssorbed raffinate is continuously withdrawn from the downstream point ofzone I (also the upstream point of zone 1V) through flow conduit 56,through rotary valve 79 and finally enters rafiinate fractionator 57. Anoverhead fraction is removed from fractionator 57 through flow conduit58 Where it enters overhead receiver 59. A portion of the overheadfraction is returned to fractionator 57 as reflux by means of flowconduit 60. The remaining overhead portion is withdrawn through flowconduit 61 where it subsequently enters flow conduit 78 and comprises aportion of the desorbent. The bottoms fraction is removed fromfractionator 57 through flow conduit 62 where a portion flows throughflow conduit 63 and heater 64 and returns to fractionator 57 by means offlow conduit 65. The net bottoms stream is withdrawn through flowconduit 66 and consists of high octane gasoline.

Selectively sorbed sorbate is continuously withdrawn from sorbentcontacting chamber 80 at the downstream point of zone III (also theupstream point of zone 11) where it enters flow conduit 67, passesthrough rotary valve 79 and finally enters sorbate fractionator 68. Anoverhead fraction is removed from fractionator 68 through flow conduit69 where it enters overhead receiver 70. A portion of the overheadfraction is returned to fractionator 68 as reflux by means of flowconduit 71. The remaining portion is withdrawn through flow conduit 72where it subsequently enters flow conduit 78 and comprises the remainingportion of the desorbent. The bottoms fraction is removed fromfractionator 68 through flow conduit 73 where a portion flows throughflow conduit 74, heater 75 and returns to fractionator 68 by means offlow conduit 76. The net bottoms stream is withdrawn through flowconduit 77 and comprises normal paraflins in the gasoline boiling range.This particular flow scheme employs a desorbent of lower boiling rangethan the gasoline, It should be observed that a desorbent heavier thangasoline could also be employed in which case the recovered productswould come overhead from these fractionators.

A continuous stream of circulating fluid is maintained in sorbentcontacting chamber 80 by means of flow conduits 52, 53 and and pump 54.The points of introduction of feed and desorbent and the withdrawal ofraffinate and sorbate are periodically shifted downstream by means ofrotary valve 79. It should be observed that the position of the zoneswill shift as the points of introduction and withdrawal are shiftedsince the zones are defined from the point of introduction andwithdrawal of the various streams. It is the continuous periodicshifting of the inlet and outlet streams to different points in thesorbent contacting chamber which results in the simulated countercurrentflow of solid sorbent and liquid.

The recovered normal paraflins could be recycled to reforming reactor35, thereby isomerizing, hydrocracking and dehydrocyclizing the normalparafiins to high octane material giving enhanced gasoline yield, or thenormal paraflins may be recovered as a useful product. Since one of theprincipal objects of this invention is to avoid excess production ofbutane, preferably the normal paraflins are not recycled unlessadditional butane is required to satisfy the vapor pressure requirementof the finished gasoline. Normal paraffins have excellent bumingqualities and are also useful as an intermediate in the production ofchemicals, polymers and plasticizers.

Example I the reactor variable conditions were operated as follows:

catalyst peak temperature, 825 F.; pressure, 2000 p.s.i.g.;

I liquid hourly space velocity, 0.5; and hydrogen circulation rate,50,900 s.c.f./bbl. A material balance was run around this step of theprocess and resulted in the follow ing yield breakdown: 53.5 s.c.f. ofmethane/bbl. of charge, 44.5 s.c.f. ethane/bbl., 78 s.c.f. propane/bbl.,7.8 liquid volume percent butane of feed, 5.6 liquid volume percentpentane, 9.8 liquid volume percent hexane and 95.3 liquid volume percent0 fraction. It is estimated that the Engler distillation end point ofthe 0 fraction was about 580 F. The normally liquid efiluent waswithdrawn through flow conduit 11 where it was fractionated infractionators 12 and 23 and produced a gasoline boiling range materialflowing in flow conduit 27 having the following properties: API gravity,55.3; Engler initial boiling point, 190 F.; Engler end point, 400 F.;paraflin content, 45 volume percent; naphthene content, 49 volumepercent; and aromatic content, 6 volume per cent.

Reforming reactor 35 was loaded with cc. of reforming catalyst Weighing51.3 grams. The above described gasoline boiling range material passingthrough flow conduit 27 was introduced into reforming reactor 35 at arate of 198 cc. per hour (measured at 60 F.) while the reactor viableconditions were operated as follows: average catalyst temperature, 883F.; pressure, 400 p.s.i.g.; liquid hourly space velocity, 1.98; andhydrogen to oil mole ratio, 10.7. A material balance was around thisstep of the process and resulted in the following yield breakdown; 930s.c.f. of hydrogen per bbl. of reformer feed, 80 s.c.f. methane/bbl., 45s.c.f. ethane/bbL, 60 s.c.f. propane/bbl., 4.1 liquid volume percentbutane of reformer feed, 3.7 liquid volume percent pentane and 82.5liquid volume percent C fraction. It is estimated that the octane numberof the C reformate is 88.0 F-l clear and the C fraction is 88.3 F-lclear. The normally liquid reactor efiiuent is introduced intostabilizer 42 which is operated as a depentanizer. The C fraction iswithdrawn through flow conduit 51 whereupon it is introduced intosorbent contacting chamber 80.

The desorbent flowing in flow conduit 78 comprises normal butane. Thehigh octane gasoline is withdrawn in flow conduit 66. It is estimatedthat the F-1 clear octane number has increased from 88.3 to 96.3 whilethe C gasoline yield has decreased from 82.5 to 75.6 liquid volumepercent as a result of processing through the sorbent contactingchamber.

It is further estimated that if the reformer severity had been increasedto directly achieve the F-1 clear 96.3 octane number on the 0 fraction,typical yields would have been as follows: 78 s.c.f. ethane/bbL, 84s.c.f. propane/bbl., 6.0 liquid volume percent butane and 75.2 liquidvolume percent (3 fraction. It should be noted that the production oflight hydrocarbons such as ethane, propane and butane has increasedWhile the overall yield of gasoline has remained relatively constant.This means in the overall results that instead of producing lighthydrocarbons having a low dollar value, a stream of high purity normalparafiins has been obtained having a much higher value by operating thereforming reactor at mild operating conditions.

I claim:

1. A combination process for the production of high octane gasoline froma heavy hydrocarbon feed stock accompanied by minimum butane productionwhich comprises:

(a) introducing said heavy hydrocarbon feed stock into contact with ahydrocracking catalyst in the presence of hydrogen in a hydrocrackingreaction zone;

(b) withdrawing a hydrocracking reactor efiiuent from said reaction zoneand separating said efiluent by fractionation to produce a gasolinefraction suitable for reforming;

(c) introducing said fraction into contact with a reforming catalyst inthe presence of hydrogen, and in the absence of recycled normalaliphatic hydro- 10 carbons, in a reforming reaction zone whilemaintaining said reforming zone at mild reforming conditions including atemperature of 800-980 F.;

(d) withdrawing from said reforming reaction zone a normally liquidreformate of moderate octane number;

(e) simultaneously introducing said reformate and a desorbent into asorption unit containing a fixed bed of molecular sieve adsorbent havinguniform pore openings of about 5 Angstroms while maintaining saidsorption unit at a temperature of from F. to about 380 F. and under apressure sufficient to maintain liquid phase conditions therein;

(f) withdrawing from said sorption unit a first stream consisting ofrelatively less sorbed rafiinate having a high octane number inadmixture with said desorbent;

(g) simultaneously withdrawing from said sorption unit a second streamconsisting of selectively sorbed sorbate having a high concentration ofnormal aliphatic hydrocarbons in admixture with said desorbent; and

(h) separately subjecting said first and second streams to fractionationto recover a high octane gasoline stream as one product and a normalaliphatic hydrocarbon-rich stream as another product.

2. The process of claim 1 further characterized in that said reformingcatalyst comprises alumina, platinum and a halogen selected from thegroup consisting of chlorine and fluorine combined therewith, and saidsorbent is Type A zeolite.

3. The process of claim 2 further characterized in that thehydrocracking reaction zone contains two zones, the first zonecontaining a Group VI and a Group VIII metal on a silica-aluminacatalyst and the second zone containing a Group VIII metal on acrystalline aluminosilicate catalyst.

4. The process of claim 1 further characterized in that the desorbent isa normaHy liquid hydrocarbon having an appreciable amount of normalaliphatic hydrocarbons and a boiling range outside of the gasolineboiling range.

References Cited UNITED STATES PATENTS 3,008,895 11/1961 Hansford et al.208-68 3,081,255 3/1963 Hess et a1. 208--88 3,159,564 12/1964 Kelley eta1. 20859 ABRAHAM RIMENS, Primary Examiner.

1. A COMBINATION PROCESS FOR THE PRODUCTION OF HIGH OCTANE GASOLINE FROMA HEAVY HYDROCARBON FEED STOCK ACCOMPANIED BY MINIMUM BUTANE PRODUCTIONWHICH COMPRISES: (A) INTRODUCING SAID HEAVY HYDROCARBON FEED STOCK INTOCONTACT WITH A HYDROCRACKING CATALYST IN THE PRESENCE OF HYDROGEN IN AHYDROCRACKING REACTION ZONE; (B) WITHDRAWING A HYDROCRACKING REACTOREFFLUENT FROM SAID REACTION ZONE AND SEPARATING SAID EFFLUENT BYFRACTIONATION TO PRODUCE A GASOLINE FRACTION SUITABLE FOR REFORMING; (C)INTRODUCING SAID FRACTION INTO CONTACT WITH A REFORMING CATALYST IN THEPRESENCE OF HYDROGEN, AND IN THE ABSENCE OF RECYLED NORMAL ALIPHATICHYDROCARBONS, IN A REFORMING REACTION ZONE WHILE MAINTAINING SAIDREFORMING ZONE AT MILD REFORMING CONDITIONS INCLUDING A TEMPERATURE OF800-980*F.; (D) WITHDRAWING FROM SAID REFORMING REACTION ZONE A NORMALLYLIQUID REFORMATE OF MODERATE OCTANE NUMBER;